Alkoxy disubstituted hydroquinones

ABSTRACT

PHOTOGRAPHIC DEVELOPING AGENTS WHICH CNSIST OF PARTICULAR ALKOXY DISUBSTITUTED HYDROQUINONES EITHER AS A SOLE DEVELOPING AGENT OR IN COMBINATION WITH OTHER PHOTOGRAPHIC DEVELOPING AGENTS PROVIDE INCREASED MAXIMUM DENSITY AND CONTRAST WITHOUT UNDESIRED INCREASE IN MINIMUM DENSITY OF DEVELOPED IMAGES. THESE DEVELOPING AGENTS ARE ESPECIALLY SUITABLE IN PHOTOGRAPHIC ELEMENTS, PROCESSES AND/OR DEVELOPER COMPOSITIONS IN DIFFUSION TRANSFER SYSTEMS.

United States Patent 0 3 591,376 ALKOXY DISUBSTITUTED HYDROQUINONES Burton D. Wilson and Derek D. Chapman, Rochester,

N.Y., assignors to Eastman Kodak Company, Rochester N.Y. No Drawing. Filed Aug. 27, 1968, Ser. No. 755,720 Int. Cl. G03c 5/54, 5/38, 5/30 U.S. Cl. 96--29 12 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION Field of the invention This invention relates to photographic developers having a developing agent which is an alkoxy disubstituted hydroquinone and to processes using this developer. In one aspect this invention relates to photographic diffusion transfer processes and to developers and developing agents used in such processes.

The prior art In recent years, diffusion transfer photographic processes have become of increasing commercial significance. The main advantage of the diffusion transfer process is that a positive print can be produced in a single step without resort to separate and inconvenient processing steps. Briefly, the diffusion transfer process is characterized by the use of a combination of a photographic emulsion layer and an image receiver or silver precipitating layer adjacent to each other. After exposure of the photographic layer, typically a developer composition is applied between the exposed photographic layer and the silver precipitating layer. The developer composition usually contains a silver halide solvent, such as sodium thiosulfate, which causes the unexposed silver salts, usually halides, to dissolve and diffuse to the silver precipitation layer where a precipitating agent within that layer causes the silver to be precipitated from the soluble silver complexes. Diffusion transfer photographic processes are well known and further details thereof are described in the literature, for example, US. Pats. 2,698,237 of Land issued Dec. 28, 1954; 2,647,- 056 of Land issued July 28, 1953; 3,108,001 of Green issued Oct. 22, 1963; and 3,345,166 of Land issued Oct. 3, 1967.

One of the primary problems concerning such processes is to obtain suitable developing agents which satisfy the stringent requirements of such systems. In order for a developing agent to be suitable for this type of process, the developing agent must be relatively quick acting and yet at the same time produce a good combination of photographic properties, e.g., high and low density, and contrast without undesired fog and/or stain. Some of the conventional developing agents used in such processes are hydroquinone and methylhydroquinone. While these developing agents are suitable in some cases, it has been desirable to obtain developing agents which are quicker acting and at the same time produce better maximum and minimum densities and contrast.

One of the primary difficulties in selecting suitable diffusion transfer developing agents resides in the fact that suitability as a conventional developer does not neces 3,591,376 Patented July 6, 1971 sarily provide success as a diffusion transfer developer. Thus, until the developing agent is actually tried one cannot be sure of its success or the degree of such success. Similarly, the fact that the structure of a given compound appears to indicate that the compound would possess a developing capacity does not indicate that the compound will possess a developing capacity sufficiently great for use in diffusion transfer processes; and, the fact that one class of compounds possesses suitable developing activity does not portent that all substituted classes of that compound will also possess suitable developing capacities. Thus, for example, the fact that hydroquinone and methylhydroquinone can be used as diffusion transfer developers does not indicate that other substituted hydroquinones would also be suitable.

US. Pat 3,345,166 of Land et a1. issued Oct. 3, 1967, and U8. Pat. 2,647,056 of Land issued July 28, 1963, suggest, respectively, the use of 2,S-dimethylhydroquinone, 2,6-dimethylhydroquinone and 2,5-ditertiarybutylhydroquinone as diffusion transfer developing agents. We have found disubstituted ethyl, isopropyl, methyl, ethyl and butyl hydroquinones also to be suitable developing agents. However, we found the disubstitution of higher alkyl groups to reduce developing power rather than increase it, possibly because we have found that such groups tend to reduce the solubility of the compound.

There accordingly has been a need for suitable developing agents which are more effective than hydroquinone or methylhydroquinone in diffusion transfer elements and processes.

OBJECT S AND SUMMARY OF THE INVENTION Objects It is, therefore, an object of the invention to provide improved diffusion transfer elements, processes and de velopers and means for obtaining such elements, processes, and developers.

Further objects will be apparent, and in part obvious, from the following description and the appended claims.

Summary of the invention In summary, the invention comprises a photographic developer composition, particularly for use in diffusion transfer systems, element, and/ or diffusion transfer process employing a developer comprising a photographic silver salt developing agent having the following formula:

I OH

wherein R is alkoxy containing 1 to 5 carbon atoms, such as methoxy, ethoxy, propoxy, butoxy and pentoxy; 'ine of R R and R is:

(21) alkyl, especially alkyl containing 1 to 5 carbon atoms, such as methyl, ethyl, propyl, butyl and pentyl,

(b) alkoxy containing 1 to 5 carbon atoms, as described,

(c) phenyl, including phenyl and phenyl containing substituent groups which do not adversely affect the desired developing activity, such as alkylphenyl, especially 1 to 5 carbon alkyl substitued phenyl, e.g., p-tolyl, xylyl, ethylphenyl and butylphenyl,

(d) a Mannich base of the formula:

wherein R and R are the same or different and each is alkyl containing 1 to 5 carbon atoms, as described, or a Mannich base of the formula:

wherein R' represents atoms completing a heterocyclic ring, such as atoms completing a 5 or 6 member ring, e.g., morpholino, piperidino (C H N), or succinimido, the remaining R R or R being hydrogen; which provide rapid developing activity, increased maximum density, lower minimum density ,and better contrast than closely related hydroquinone developing agents, e.g., than hydroquinone or methylhydroquinone.

The invention also comprises a photographic developer composition, element and/or diffusion transfer process employing one or more other developing agents, as for, example, 2,4-diarnino-o-cresol, also known as 2,4-diamino-6-methyl phenol, and its salts, e.g., hydrochloride or sulfate salts; S-pyrazolidone developing agents, e.g., 1- phenyI-B-pyrazolidone or 4,4-dimethyl-l-phenyl3-pyrazo lidone, and the like, in combination with the described developing agent of Formula I. Developers of the invention comprise the developing agents described along with other various components conventional to diffusion transfer developers.

DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS In accordance with the invention, a class of disubstituted hydroquinones have been found to be particularly good diffusion transfer developing agents and auxiliary developing agents for developing photographic silver salt latent images. The class of disubstituted hydroquinones used in the practice of the invention can be represented by the following para-, meta-, and ortho-formulas:

(II) (|)H (III) 11 (1V) OH -R 1341- R R and R R O H O H O H para meta ortho wherein R, R R and R are as described for Formula I.

As is readily apparent, the above Formulas II, III and IV differ from each other only in the position of R R and R with respect to the position of R; thus, alternatively the three formulas can be conveniently expressed in terms of a single generic formula, i.e., Formula I as described.

The following compounds have been found to give good results and are illustrative of compounds falling within the scope of this formula:

2,5 -dimethoxyhydroquinone 2,6-dimethoxyhydroquinone Z-methoxy-S-methylhydroquinone 2-methoxy-5- (morpholinomethyl hydroquinone and 2-methoxy-5-phenylhydro quinone This listing is, of course, only exemplary and the full range of compounds encompassed by generic Formula I can be used in the practice of the invention.

The various compounds falling within the generic formula can be prepared by methods known in the art or by obvious modification or adaptation of known methods. For purposes of illustration a few of these compounds and their method of preparation are as follows:

2-methoxy-5-(morpholinomethyl)hydroquinone can, for example, be prepared by admixing about equal molar quantities of paraformaldehyde and morpholine. The resulting mixture is then heated at a temperature of about 50 to 100 C. until a homogeneous mixture forms and then cooled and mixed with a stoichiometric quantity of hydroquinone, preferably in a solvent such as, for example, acetone, equal to the stoichiometric quantity of paraformaldehyde or morpholine in the initial reaction mixture. The mixture is then aged at about room temperature until reaction is completed, usually about from 3 to 5 hours. The resulting 2-methoxy-5-(morpholinomethyl)hydroquinone product is then separated from the solvent and unreacted reactants and/or side reaction products. The separation can conveniently be carried out by evaporation of the unwanted materials. The product can be further purified by conventional recrystallization procedures. Z-propanol is a suitable solvent for this recrystallization. Z-methoxy-S-methylhydroquinone can be prepared by hydrogenating 2-methoxy-5-(morpholinomethyl) hydroquinone over a palladium catalyst at a temperature of about from 50 to C. and a pressure of from 30* to 100 pounds per square inch until about 1 mole of hydrogen is consumed per mole of Z-methoxy-S-(morpholinomethyl)hydroquinone and then adding about 1 mole of 1 molar hydrochloric acid per mole of hydrogen consumed. A purified form of the product can then be obtained by dissolving the impure product in Water and then extracting the product with a suitable extracting agent such as, for example, ether, chloroform and the like. The product can be further purified by recrystallization. Suitable solvents which can be used for this purpose include mixtures of chloroform and petroleum ether, ether/ petroleum ether and the like.

2-methoxy-5-phenylhydroquinone can be prepared by oxidizing 3-hydroxy-4-methoxybiphenyl to 2-methoxy-5- phenylbenzoquinone using any of the processes of the prior art conventionally used for this purpose. The 2- methoxy-5-phenylbenzoquinone product can then be further purified by recrystallization from a suitable solvent such as, for example, ethanol, methanol and the like. The desired 2-methoxy-S-phenylhydroquinone product of the invention can then be prepared by catalytically reducing the recrystallized 2-methoxy-S-phenylbenzoquinone over a palladium catalyst at a temperature of about from 30 to 40 C. and at a presence of about 30 to 40 pounds per square inch, and the resulting Z-methoxy-S-phenylhydroquinone can then be further purified by recrystallization from a suitable solvent such as benzene.

The disubstituted hydroquinone developing agents, as described according to the invention, can be used either as the sole developing agent or in conjunction with one or more other developing agents. They can be used as an auxiliary developing agent in conjunction with one or more other developing agents if desired or, one or more other developing agents can be used as auxiliary developing agents with the described disubstituted hydroquinone developing agents of the invention. Also mixtures of the described disubstituted hydroquinones can be used.

One embodiment of the invention comprises in a photographic developer composition, especially one suitable for use in diffusion transfer systems, comprising (a) a silver halide solvent and (b) at least one photographic silver salt developing agent, the improvement comprising a photographic silver salt developing agent according to Formula I as described.

A wide range of silver halide solvents can be employed. These include any of those suitable in diffusion transfer systems which provide an image transfer without undesired stain, lower maximum density or other undesired properties. While silver halide solvents suitable for diffusion transfer systems are especially desirable, other silver halide solvents can be employed if desired. Suitable silver halide solvents, include thiosulfates, for example, sodium thiosulfate, thiocyanates, such as sodium thiocyanate, potassium thiocyanate, or ammonium thiocyanate, uracils, thioethers and the like, as set out in the described prior art.

The developer composition can contain additional developing agents, either as auxiliary developing agents or as the main developing agent. These include, for example, polyhydroxybenzene developing agents such as hydroquinone developing agents, for example, hydroquinone,

catechol and pyrogallol; chloro substituted hydroquinones such as chlorohydroquinone or dichlorohydroquinone; alkoxy substituted hydroquinones such as methoXy hydroquinone or ethoxy hydroquinone; aminophenol developing agents, such as 2,4-diaminophenols, including 6- methyl-2,4 diaminophenol, and methylaminophenols; ascorbic acid; pyrazolidone developing agents such as lphenyl-3-pyrazolidone, including those described in Kodak British Pat. 930,572 published July 3, 1963, and U.S. Pat. 2,751,297 of Hood and Crookshank issued June 19, 1956, and acyl derivatives of p-aminophenol such as described in Kodak British Pat. 1,045,303 published Oct. 12, 1966.

These developing agents can be employed in various combinations or mixtures. Also they can be in any suitable location in the system, such as in a photographic layer, a layer contiguous to a photographic silver salt, a developer composition, an image receiving layer, an overcoat layer and/or other layer. If a combination of developing agents is employed, one developing agent can be in one location in the system, such as in a layer of a photographic element and another developing agent of the combination can be in another location in the system, if desired, such as in a developer composition and/or image receiver layer.

The suitable developing agent concentration will vary widely depending on the particular developing agent used, the nature of the silver halide emulsion to be developed, the particular result desired and other factors described. Usually the total developing agent concentration will fall within the range of about from .1 to .5 gram moles per liter in the case of a liquid developer composition. Optimum concentration for a given application can be obtained by routine experimentation.

Development activators, such as those commonly employed in silver halide developer compositions, can be employed with the developing agents of the invention. Since generally the developer must be alkaline to effect efiicient reduction of a silver halide latent image, the developer must either include a development activator or an activator must be added to activate the developing agents. Suitable development activators include inorganic alkalies such as lithium hydroxide, potassium hydroxide and sodium hydroxide, sodium phosphate, tribasic sodium carbonate, ammonium hydroxide, sodium metaborate, sodium borate, and/or organic development activators such as organic amines, and/or alkali releasing materials and the like. The purpose of these activators, as is well known, is to raise the pH to a level at which the developing agent will be effective to reduce the silver halide latent image, i.e., above a pH of about 7. The most eflicient pH range for any given developer can be determined by routine experimentation. Generally, an excess of activator is used to ensure that the correct pH is maintained. Buffered activators are particularly advantageous for this purpose.

The developer, though commonly employed as an aqueous solution, can be employed in any form suitable for developing an exposed photographic element. They can be supplied as an aqueous silver halide developer solution or liquid concentrate; as a component of a solid composition, such as a powder, suitable for dissolving in a solvent such as an aqueous solvent; as a viscous composition, e.g., containing various thickening agents; as a packaged component of a kit for mixing with various processing agents; or as a component of a fusible solid, such as, a solid containing a homogeneous mixture of an alkylene oxide polymer and a developing agent used in the practice of the invention, which melts above room temperature.

Where the developer composition is designed for diffusion transfer systems, the developer for best results is typically relatively viscous. This renders the developer more managable from a handling standpoint and also retards migration of the soluble silver complexes formed by the action of the silver solvent upon the unexposed silver salts in the emulsion layer of the photographic element. The viscosity should for best results be about from to 10,000 cps. at a temperature of from 10 to 30 C. Usually a thickening agent must be added to obtain the desired viscosity. A wide range of thickening agents can be used, such as hydroxy ethyl cellulose, carboxy methyl cellulose and the like. A typical diffusion transfer developer is disclosed in U.S. Pat. 3,120,795 of Land issued Feb. 11, 1964.

Frequently the developer composition for a diffusion transfer system will be contained within a separate container or capsule located between the photographic emulsion layer and the receiving layer. This container or capsule can then be conveniently ruptured or otherwise opened allowing the developer to escape between the layers. One such system is described in U.S. Pat. 2,647,056 of Land issued July 28, 1953.

Another embodiment of the invention is in an element comprising a support having at least one layer comprising at least one photographic silver salt developing agent the improvement comprising a photographic silver salt developing agent according to Formula I as described.

A wide range of elements can be employed according to the invention. This includes any support having a layer comprising a developing agent according to Formula I as described. These include, for example, photo graphic elements which comprise a support having one ore more layers comprising a radiation sensitive material such as a photographic silver salt. Also included are elements not containing a photographic silver salt. An element which is a receiver sheet or comprises an image receiver layer, such as an image receiver sheet known in the diffusion transfer art is also included.

The developing agents of the invention are. especially useful in a diffusion transfer unit. A diffusion transfer unit includes in combination (a) a photographic element containing at least one photographic layer, typically a photographic silver halide emulsion layer, suitable for diffusion transfer processing, (b) a developer composition, typically a viscous solution, containing a silver halide solvent, a development activator and a developing agent, and (c) a receiver, typically containing precipitating nuclei or materials from which nuclei can be formed, which is suitable for producing a developed image. An image is developed in such a unit typically by (1) exposing the photographic element (a) to produce a latent image, (2) placing the developer composition between the photographic element (a) and receiver (c) to cause development of the image in the photographic element (a) and formation of a diffusible image in the unexposed areas of the photographic element which transfers to the receiver (c) where it is developed by precipitation on the precipitating nuclei. The developing agent is typically employed in the developer composition, but can be in the photographic element (a), and/ or developer composition (b), and/or receiver (c).

Accordingly, the disubstituted hydroquinones, employed in the practice. of the invention can be employed in any suitable location such as incorporated into photographic elements, for example, as a component of one of the layers of a photographic element. For example, the disubstituted hydroquinones employed by the invention can be used in a photographic silver salt emulsion layer, an overcoat layer, a layer under the. emulsion layer, a baryta layer, an antihalation layer or in virtually any layer contiguous to the silver salt to be developed. While such elements are particularly useful in diffusion transfer units, they can also be used for X-ray and other nonspectrally sensitized applications or they can contain spectral sensitizing dyes such as described in U.S. Pats. 2,526,632 of Brooker et al. issued Oct. 24, 1950, and 2,503,776 of Sprague issued Apr. 11, 1950. Spectral sensitizers which can be used include cyanines, merocyanines, styryls and hemicyanines.

Various photographic salts can be used in the elements employed in the practice of the invention. These include photographic silver halides such as silver iodide, silver bromide, silver chloride, silver bromoiodide, silver chloro iodide and the like. Photographic silver salts which are not silver halides can also be employed such as silver salts of certain organic acids.

The coating or layers of photographic elements employed according to the invention are coated on a support using conventional coating means and methods. Suitable supports include, for example, cellulose acetate films, cellulose nitrate films, polyethylene terephthalate films, or other polyester films, polycarbonate films and related materials, papers, such as paper supports coated with resinous materials, e.g., cotaed with polyethylene, polypropylene and/or ethylene-butene copolymers, glass, metal and the like.

The photographic elements employed according to the invention typically contain a layer, usually an emulsion layer, comprising any of the known vehicles or binding materials suitable for photographic purposes. These include, for example, gelatin, cellulose derivatives, polymerized vinyl compounds as well as mixtures of such binding agents.

The disubstituted hydroquinone developing agents used in the practice of the invention can be employed in combination with other addenda known in the art to be useful in or for processing photographic elements. For instance, the photographic elements and/ or other compositions of the invention can contain various photographic addenda, particularly those known to be beneficial in photographic compositions. The various addenda and concentrations to be employed can be determined by those skilled in the art. Suitable photographic addenda include hardeners, e.g., those set forth in Agfa British Pat. 974,317, published Nov. 4, 1964; buffers which maintain the desired developing activity and/or pH level; coatings aids; plasticizers; speed-increasing addenda, such as quaternary ammonium salts and alkylene oxide polymers; and various stabilizing agents, such as sodium sulfite.

The disubstituted hydroquinone developing agents of the invention can be used in colloid transfer processes and elements such as described in U.S. Pat. 2,596,752 of Williams issued May 13, 1952. They can also be used in layers of photographic elements intended for use in monobath processing such as described in U.S. Pat. 2,875,- 048 of Haist el al. issued Feb. 24, 1959, and in web type processing such as described in U.S. Pat. 3,179,517 of Tregillus et al. issued Apr. 20, 1965.

The disubstituted hydroquinone developing agents used in the practice of the invention can also be employed in the layers of photographic elements designed for stabilization processing. For example, they can be incorporated in one or more layers of a photographic element which is exposed, activated by contact with an activator, such as an alkaline solution and then contacted with a thiocyanate or thiosulfate solution, such as an ammonium thiocyanate. Such processes are described, for example, in US. Pat. 3,326,684 of Nishio et al. issued June 20, 1967, and in an article by H. D. Russell, E. C. Yackel and E. G. Grouse in the P.S.A. Journal, August 1950, pages 5962, entitled Stabilization Processing of Films and Papers.

The disubstituted hydroquinone developing agents employed according to the invention can also be present in one or more layers of a photographic element designed for recording color images. For example, these compounds can be employed in one or more layers of a photographic element containing a photographic layer sensitive to the blue region of the spectrum, a photographic layer sensitive to the green region of the spectrum, and a photographic layer sensitive to the red region of the spectrum, such as described in Mees, The Theory of the Photographic Process, 3rd edition, 1966, pages 382-396. The layers sensitive to the blue, green and red regions of the spectrum can contain any suitable sensitizing dyes.

The disubstituted hydroquinone developing agents used in the practice of the invention can be employed in a photographic element containing a dye developer. They can also be employed in processing baths and processing photographic elements containing dye developers. The developing agents of the invention can, for instance, be employed in photographic dye developer image transfer systems such as described in U.S. Pats. 3,253,915 of Weyerts issued May 31, 1966; 2,559,643 of Land issued July 10, 1951; and 2,698,798 of Land issued Jan. 4, 1955. In such systems, a dye diffusion transfer takes place. Compounds which contain, at the same molecular value, the chromonophoric system of the dye and a silver halide photographic moiety are useful compounds in photographic elements and are commonly called dye developers. Photographic elements containing such dye developers generally comprise a plurality of photosensitive silver halide emulsions wherein each of the emulsions is selectively sensitized to a different region of the spectrum. A dye developer is positioned contiguous to the silver halide of the emulsion. Such a photographic element, according to the invention, can contain an alkoxy disubstituted hydroquinone compound or compounds, according to the invention, as an incorporated developing agent or agents. Typically one of these compounds is employed in a gelatin overcoat layer. The photographic element after exposure can be processed with an alkaline composition with the latent image being developed in the image areas with the dye developers. This developer immobilizes such dye developers in such areas. The dye developers in the unexposed areas diffuse to the surface imagewise and are transferred to a reception layer or receiving sheet to form a multi-color image. Similarly, such dye diffusion transfer systems can be used to prepare single color transfer prints. The developing agents within the scope of the invention are also useful as auxiliary developers in dye developer image transfer element processes.

Silver precipitating nuclei can be present in a photographic element containing a developing agent of the invention. Such nuclei can be present in the described developer composition if desired. Suitable silver precipitating nuclei or agents which can be employed can be physical development nuclei and/ or chemical precipitants including (a) heavy metals in colloidal form and salts of these metals,

(b) salts of amines which form silver salts and/ or (c) non-diffusing polymeric materials with functional groups capable of combining with the silver amine.

Suitable silver precipitating agents and/or nuclei within the above classes include metal sulfides, sellenides, polysulfides, polysellenides, thiourea derivatives, stannous salts, silver, gold, platinum, palladium, and mercury, colloidal silver and similar agents disclosed, for example, in U.S. Pat. 3,020,155 of Yackel et al. issued Feb. 6, 1962. A wide range of concentrations of the silver precipitating agents and/or nuclei can be employed. The concentration of silver precipitant and/or nuclei in the receiving layer or receiving sheet must be at least sufficient to ensure removal of undeveloped silver salt from the light-sensitive layer to be processed to form a good image in the receiving layer. Usually, the amount is about 3 to about 320 milligrams per square foot of the layer containing the precipitants or nuclei.

A further embodiment of the invention is a process for developing silver salt latent images, which comprises contacting an exposed silver salt layer with a composition which comprises the disubstituted hydroquinone developing agents employed in the practice of the invention. According to this embodiment, the dye substituted hydroquinone developing agents can be employed in the layers of a photographic element, as before described, and then activated by a composition comprising an activating agent, or the disubstituted hydroquinone can be applied in a developer composition, such as was previously described according to the invention, either containing an activator or to which an activator is added either prior to or after contact with the latent image.

As before mentioned, the disbustituted hydroquinone is particularly suited for developing latent images in diffusion transfer systems. In a diflusion transfer process, according to the invention, the silver salt latent image can be developed by contacting it with a processing composition comprising:

(a) a development activator, (b) a silver halide solvent, and (c) a silver halide developing agent interposed between the photographic silver salt layer and an image receiving layer containing silver precipitating agents; thereby forming an imagewise distribution of silver complexes in the silver salt layer; and transferring, at least in part, the imagewise distribution of silver complexes to the image receiving layer and precipitating agents to provide a developed silver image. The processing composition used above comprises:

(a) a development activator, (b) a silver halide solvent, and (c) at least one silver halide developing agent which is an alkkoxy disubstituted hydroquinone according to the practice of the invention. These developing agents can be employed in this diffusion transfer type process as the main developing agent or as an auxiliary developing agent. Typically, the processing composition will also contain a thickening agent. Where the photographic element contains an incorporated silver halide developing agent, the concentration of developing agent in the processing composition can be suitably reduced.

The concentration of the developing agents used in the practice of the invention as described can vary over wide ranges depending upon the particular photographic results desired, the position of the developing agent in the system, for example, in the photographic element, the developer composition, etc. and other factors, such as on processing conditions, addenda present in the photographic element to be processed and/or in the processing compositions. Suitable concentrations can be determined by those skilled in the art. Typically, when a developing agent is employed in a layer of a photographic element it is employed in the concentration of about .5 to about 2 moles per mole of silver present in the photographic element. The particular developing time required can vary over a wide range between a few seconds up to an hour or more depending on the desired image, and the various addenda for its present; optimum developing time can, however, be obtained by routine experimentation. As before mentioned, the particular pH required will also vary with the particular variables within a given system but usually will be in about the range of from 9 to 13. The particular concentration of activator required to obtain the desired pH can be easily calculated or determined by routine experimentation as can also the optimum pH.

It is often advantageous to have an antifoggant present in the developer compositions of the invention and/or in the photographic element processed according to the in vention. Suitable antifoggants include organic antifogfoggants, such as benzotriazole, benzimidazole, Z-mercaptobenzimidazole and mercaptotetrazole antifoggants. The developer compositions of the invention can contain an inorganic antifoggant, such as potassium bromide, potassium iodide and/ or sodium bromide. The concentration of antifoggant in either the developer composition or in the photographic element layers can be varied depending upon the desired image, other components present, processing treatments to be used, etc. Usually less than about 2% by weight, usually about 0.01 to 2% by weight, based on the weight of the activated developing composition.

The following examples are included for a further understanding of the invention.

l 0 EXAMPLE 1 This illustrates preparation of 2,5-dimethoxyhydroquinone.

2,5 dimethoxyhydroquinone is prepared by conventional catalytic reduction of commercially available 2,5- dimethoxybenzoquinone at a temperature of 40 C. and a pressure of 40 pounds per square inch using a palladium catalyst.

EXAMPLE 2 This illustrates preparation of 2,6 dimethoxyhydroquinone.

2,6 dimethoxyhydroquinone is prepared by conventional catalytic reduction of 2,6 dimethoxybenzoquinone at a temperature of 40 C. and a pressure of 40 pounds per square inch using a palladium catalyst.

EXAMPLE 3 This example illustrates the preparation of Z-methoxy- 5-(morpholinomethyl)hydroquinone.

One mole of paraformaldehyde is mixed with one mole of morpholine and the resulting mixture is then heated together on a steam bath, at about a temperature of C., until a homogeneous mass is observed. One mole of methoxyhydroquinone dissolved in acetone is then added to the cooled homogeneous mass. This solution is then allowed to react for three hours at room temperature. The mixture is then evaporated to dryness and the product recrystallized from 2-propanol. The melting point and formula of the product is then determined using conventional laboratory techniques. The melting point for the product is about l40-l44 C. and the formula of the product is as follows:

EXAMPLE 4 This example illustrates the preparation of 2methoxy- S-methylhydroquinone.

2-methoxy-5-(morpholinomethyl)hydroquinone is hydrogenated over a palladium catalyst at a temperature of 60 C. and a pressure of 40 pounds per square inch until one mole of hydrogen is consumed. One mole of 1 molar hydrochloric acid is then added and the solution evaporated to dryness. The resulting product is then dissolved in water and extracted with ether. The extracted product is then dissolved in a mixture of chloroform and petroleum ether and then recrystallized. The melting point and formula of the recrystallized product is then determined using conventional laboratory techniques. The melting point of the product is between l26-l27 C. and the formula of the product is as follows:

bit

EXAMPLE 5 This example illustrates the preparation of Z-methoxy- S-phenylhydroquinone.

In this example 3-hydroxy-4-methoxybiphenyl is oxidized to 2-methoxy-5-phenylbenzoquinone by conventional oxidation processes. The Z-methoxy-S-phenylbenzoquinone is then recrystallized from ethanol. The recrystallized benzoquinone is catalytically reduced to 2-methoxy-S-phenylhydroquinone by catalytic reduction over a palladium catalyst at a temperature of 3040 C., and

1 l at a pressure of 30-40 pounds per square inch. The resulting product is then recrystallized from benzene to further purify it. The melting point and formula of the product is then determined using conventional laboratory tech- 12 actuality should be considered as having lower speeds than the developers having higher contrasts.

The results of these tests are summarized in the following Table I.

TABLE I Example Relative Number Developing agent Dmnx. miu. 7 speed 7 Hydroquinone (prior art) 0. 1 8 Methylhydroquinone (prior art) 0.79 0. 0. 47 Z (251) 9 2,S-dimethoxyhydroquinone 1. 53 0.15 0. 78 100 10 2-methoxy-5-methylhydroquinone 1.36 0.00 0.99 141 11 2-methoxy-5-(morpholinomethyl)hydroqu on 1. 22 0.00 0.80 102 1 No image under the test conditions.

2 Tested at 0.6 above fog.

niques. The melting point of the product is 103-104 C. and the formula is determined to be as:

in [Doom EXAMPLE 6 EXAMPLES 12-18 In the following examples the photographic developing properties of the compounds of Examples 1-5 as primary developing agents when used in conjunction with an auxiliary developing agent are determined and compared with the conventional developers hydroquinone and methylhydroquinone also used as primary developing agents with the same auxiliary developing agent.

Various developer samples are prepared in the same manner as Example 6, having a primary developing agent concentration of 0.25 mole per liter and an auxiliary developing agent concentration of 0.05 mole per liter. The auxiliary developing agent used is 2,4-dia-rnino-o-cresol, also known as 6-methyl amidol and 2,4-diamino-6-methyl phenol. Also, suificient sodium hydroxide is added to neutralize any acid introduced with the auxiliary develop ing agents.

The various samples are tested in the same manner as in Example 6. The results of the tests are summarized in the following Table II.

TABLE II Example Relative Number Developing agent Dm Dmin. Gamma speed 12 Hydroquinone (prior art) 0. 56 0. 00 0. 43

Methylhydroquinone (prior art)..- 0.68 0. 01 0. 61 2 (562 2,5-dimethoxyhydroquinone 1. 53 0. 0. 67 2 (40) 2,6-dimethoxyhydroqninone 1. 43 0. 01 1. 01 162 2-methoxy-5-methylhydroquinone 1. 28 0.01 1. 14 102 2-methoxy-5(morpholinomethyl)hydroquinone 1. 18 0. 00 0. 91 105 18 2-n1etl10xy-5-phenylhydroquinone 1. 08 0.01 0.77 178 indeterminate.

2 Tested at 0.6 above fog.

iodide; 59 grams of sodium hydroxide; 330 grams of hydroxyethylcellulose; and then adding sufficient water to form one liter of solution.

EXAMPLES 7-11 In the following examples, the photographic developing properties of the compounds of Examples 1-4, as sole developers, are tested and compared with the known developing agents hydroquinone and methylhydroquinone.

Various developers are prepared by adding the particular developing agents to be tested, to respective samples of the developing carrier solution of Example 6, in a quantity suificient to provide a developing agent concentration of 0.30 mole per liter. The respective samples are then tested in a diffusion transfer system by spreading them between an exposed silver halide layer and an image receiving sheet. The silver halide layer to be used is a silver bromoiodide emulsion coated at 144 milligrams of silver per square foot on a paper support. A palladium nuclei image receiving sheet is used. The respective tests are conducted under identical conditions. The receiving sheets are then tested for density (maximum and minimum), contrast and speed by standard testing procedures.

In cases where the contrast (7) is low, the relative speeds are measured at 0.6 above fog and thus are abnor nially high and have very little comparative value and in As can be seen from Tables I and II, the developing agents of the invention are particularly desirable for diffusion transfer systems yielding both an increase in speed and an improved picture quality, i.e., higher D with low D and more importantly higher contrast, over the conventional hydroquinone, and methylhydroquinone developers of the prior art.

Mannich base used herein, is a known term and includes a compound prepared by a Mannich reaction, such as described in Chemistry of Organic Compounds by C. R. Noller, 3rd edition, pages 494-495. A Mannich base in general is prepared by condensation of ammonia or a primary or secondary amine with a compound having an active hydrogen atom, such as a hydroquinone. The active hydrogen atom is replaced by an aminomethyl group or substituted aminomethyl group.

The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

We claim:

1. A photographic silver halide developer composition comprising (a) a silver halide solvent, (b) at least one photographic silver halide developing agent the improve- 13 ment wherein said photographic silver halide developing agent is of the formula:

wherein R is alkoxy containing 1 to carbon atoms, one of R R and R is (i) alkyl containing 1 to 5 carbon atoms,

(ii) alkoxy containing 1 to 5 carbon atoms,

(iii) phenyl and alkylphenyl, or

(iv) a Mannich base ('I) of the formula:

wherein R" and R are each alkyl containing 1 to 5 carbon atoms or (II) of the formula wherein R represents atoms completing a 5 or 6 membered heterocyclic ring, the remaining R R and R being hydrogen and (c) an alkaline development activator.

2. The composition of claim 1 wherein said silver salt developing agent is selected from the group consisting of 2,5-dimethoxyhydroquinone, 2,6-dimethoxyhydroquinone, Z-methoxy-S-methylhydroquinone, 2-methoxy-5- (morpholinomethyl) -hydro quinone, 2-methoxy-S-phenylhydroquinone, and mixtures thereof.

3. The composition of claim 1 wherein said composition also comprises a thickening agent in sufiicient concentration so that the viscosity of said composition at about 10 C. to about C. is from about 100 to about 10,000 cps.

4. The composition of claim 3 wherein said thickening agent is selected from the group consisting of hydroxyethyl cellulose, carboxymethyl cellulose and mixtures thereof.

5. The composition of claim 1 wherein said composition also comprises at least one other silver halide developing agent.

6. The composition of claim 5 wherein said other developing agent is selected from the group consisting of polyhydroxybenzene, aminophenol, and pyrazolidone developing agents and mixtures thereof.

7. The composition of claim 1 wherein said composition also comprises an antifoggant.

8. The composition of claim 1 wherein said composition comprises a liquid and has a developing agent concentration of about .1 to .5 mole per liter.

9. The composition of claim 1 wherein said composition is a viscous aqueous solution consisting essentially of about:

22 grams of sodium sulfate 84 grams of sodium thiosulfate pentahydrate 30 grams of potassium bromide 0.8 gram of potassium iodide 59 grams of sodium hydroxide 30 grams of hydroxyethylcellulose per liter of solution,

and about 0.3 mole per liter of a developing agent selected from the group consisting of 2,S-dimethoxyhydroquinone, 2-methoxy-5-methylhydroquinone and 2-methoxy-5- (morpholinomethyl)hydroquinone.

10. The composition of claim 1 wherein said composition comprises an auxiliary developing agent and wherein said composition is a viscous aqueous solution consisting essentially of about:

14 22 grams of sodium sulfate 84 grams of sodium thiosulfate pentahydrate 30 grams of potassium bromide 0.8 gram of potassium iodide 59 grams of sodium hydroxide 30 grams of hydrox'yethylcellulose per liter of solution and about 0.25 mole of a developing agent selected from the group consisting of: 2,S-dimethoxyhydroquinone 2,6-dimethoxyhydroquinone Z-methoxy-S-methylhydroquinone 2-methoxy-5- (morpholinomethyl hydroquinone and 2-methoxy-5-phenyl hydroquinone and about 0.05 mole per liter of 2,4-diamino-o-cresol as an auxiliary developing agent. 11. In a photographic silver salt diffusion transfer process comprising the steps of developing a latent image in an exposed photographic silver halide element; contacting undeveloped photographic silver halide with a silver halide solvent forming an imagewise distribution of soluble silver complex in unexposed areas of said element; transferring at least part of said soluble silver complex to a receiving layer and precipitating said transferred image to produce a reversed developed image; the improvement comprising developing said latent image with a developing agent of the formula:

wherein R is alkoxy containing 1 to 5 carbon atoms, one

R1, R2, and R3 iS (i) alkyl containing 1 to 5 carbon atoms,

(ii) alkoxy containing 1 to 5 carbon atoms,

(iii) phenyl and alkylphenyl, or

(iv) a Mannich base (I) of the formula:

wherein R" and R are each alkyl containing 1 to 5 carbon atoms or (II) of the formula:

References Cited UNITED STATES PATENTS 10/1963 Green 9629 8/1966 Weyerts et al. 96-29 NORMAN G. TORCHIN, Primary Examiner M. F. KELLEY, Assistant Examiner US. Cl. X.R. 966l, 66 

